1. Field of the Invention
This invention relates to an inflatable type occupant restraint system comprising an air bag module assembly which is provided in automobile or other automotive vehicles for the protection of the driver and/or passengers in the event of a collision. More particularly, the invention relates to an improvement in the method and means provided for holding the air bag or cushion in the air bag module assembly.
2. Description of the Related Art
The assembly of an air bag module involves the manufacture, installation and checking of many components. Among such components that are common to all air bag modules are the cover, a cushion, cushion holder means including an annular retainer or retaining ring, a supporting plate such as a module housing or mounting plate, fasteners, a gas generator or inflator, and means to attach the assembly to a steering wheel, dashboard or another appropriate part of the vehicle.
In such air bag modules, a central inflating gas inlet opening of an air bag cushion is held, that is, clamped, between a flange of an inflator and an annular retaining ring through a module housing or mounting plate. Rivets or other fasteners are used to attach the retaining ring to the gas inlet opening of the cushion. The edge of the opening of the cushion is disposed in a substantially even manner with the inner circular edge of the retaining ring. The retaining ring with the air bag cushion affixed thereto is then bolted to the module housing and the flange of the inflator with the inflator so arranged that the flange thereof is positioned externally of the cushion and the module housing.
The force holding the air bag cushion to the inflator and module housing is concentrated in the shearing resistance of that part of the cushion which has a width corresponding to the diameter of the rivet or other fastener and a length corresponding to the distance from the rivet to the edge of the gas inlet opening of the air bag cushion.
The use of rivets to attach the air bag cushion to the retaining ring and thereby to the module housing and inflator is a major cause of reworking inflator module assemblies in the manufacture thereof. When reworking is not possible, the defective, air bag modules must be discarded. This results in lost production and increased cost of manufacturing. The non use of the retaining ring and associated rivets or other fasteners in the manufacture of the air bag module assembly would eliminate a major cause for reworking and disposal of defective inflator modules.
Thus, there is a need and a demand for the provision of a better and a less costly means of air bag cushion retention in an air bag module assembly. The present invention was devised to fill the gap that has existed in the art in this respect.